Following images represent two cases of fetal D-transposition of great arteries. Both cases were diagnosed at 20 weeks of pregnancy and the mothers were primigravidas with negative family history.

Images 1, 2: The images represent drawings explaining principle of the D-transposition of the great arteries. The anomaly results from failure of spiralization of truncoconal septa during embryonic development of the heart (approximately between the 5th and 9th weeks). The lack of spiralization of the truncoconal septa leads to parallel arrangement of the outflow tracts and abnormal connection of the pulmonary artery and aorta to their corresponding ventricles - that means the aorta arises from the right ventricle and the pulmonary artery arises from the left ventricle. This abnormal arrangement causes that the left ventricle empties into the pulmonary circulation and the right ventricle empties into the systemic circulation. Image 1 shows normal arrangement and crisscrossing of the great vessels; the image 2 shows parallel arrangement of the outflow tracts and abnormal connection of the aorta and pulmonary artery in cases of the transposition of the great arteries (Ao - aorta, PA - pulmonary artery, RV - right ventricle, LV - left ventricle). The parallel course of the outflow tracts in cases of the transposition of the great arteries is one of the main features of the anomaly recognizable on prenatal ultrasound.

Images 3, 4: The images show scheme of the blood circulation in the case of the transposition of the great arteries during the prenatal (image 3) and postnatal (image 4) period. Pulmonary and systemic circulations in the case of the transposition of the great arteries communicates prenatally via the foramen ovale and ductus arteriosus (image 3). Postnatally (image 4), due to closure of the foramen ovale and ductus arteriosus, the abnormal connection of the ventricles and great arteries results in two parallel circulations, where deoxygenated systemic blood circulation does not communicate with the oxygenated pulmonary circulation.

Case 1

Images 5, 6, 7, and video 1: The images 5, 6, and 7 represent still parts of the color Doppler 4D cine loop (video 1) of the heart in the case of the transposition of the great arteries. Ventricular filling (in red) and parallel course of transposed great arteries (in blue) can be seen (PA - pulmonary artery, Ao - aorta, LV - left ventricle, RV - right ventricle). Speed of the cine loop of the video 1 was decreased to 40%.

Images 8, 9, and 10: The image 8 represents sagittal 3D color Doppler image of the outflow tracts of the heart in the case of the transposition of the great arteries. Those two blue flows represent transposed aorta (more anteriorly; closer to the upper side of the image) and pulmonary artery (more posteriorly; just behind the transposed aorta). The image 9 shows sagittal 2D scan of the heart with transposed aorta (Ao) arising from the right ventricle. The image 10 shows three-vessel view of the heart in the case of transposition of the great arteries. Just transposed aorta (Ao) and superior vena cava are visible at this level.

Case 2

Images 11, 12: The image 11 shows sagittal 2D scan of the heart with transposed aorta arising from the right ventricle. The image 12 represents a fusion of the image 11 with a drawing depicting the course of the transposed aorta (in red).

Images 13, 14: The image 13 shows sagittal 2D scan of the heart with transposed aorta arising from the right ventricle and transposed pulmonary artery arising from the left ventricle and going in parallel just behind the aorta. The image 14 represents a fusion of the image 13 with a drawing depicting the parallel course of the transposed aorta (in red) and pulmonary artery (in blue).

Images 15, 16, 17, and 18: Transposition of the great arteries. The image 15 shows five-chamber view of the heart with bifurcating pulmonary artery arising from the left ventricle. The image 16 represents color Doppler scan of the heart at the same level as the image 15. Bifurcating pulmonary artery arising from the left ventricle is clearly visible. The images 17 and 18 represent fusions of the image 15 with drawings depicting the structures visible on the image 15 (RV - right ventricle, LV - left ventricle, pulmonary artery in blue).

Images 19, 20: Transposition of the great arteries. The images show three-vessel view of the heart, where just transposed aorta (depicted in red color on the image 20), and superior vena cava are visible. Direction of the blood flow within the transposed aorta is shown by the green arrow on the image 20.

Images 21, 22, and 23: Transposition of the great arteries. By these images we wanted to demonstrate how can be the transposition of the great arteries misinterpreted as normal crisscrossing of the aorta and pulmonary artery. When we sweep from the five chamber view of the heart to the three vessel view, the direction of the outflow tracts may appear crisscrossed in craniocaudal view. Compare the direction of the pulmonary artery (depicted in blue) arising from the left ventricle (LV) on the image 21, and the direction of the aorta (depicted in red color) arising from the right ventricle at the level of the three-vessel view on the image 22. The image 23 shows fusion of the images 21 and 22, so as the craniocaudal "crisscrossing" of the aorta and pulmonary artery was better visible. These vessels are parallel arrangement, when we look at them in sagittal view. This emphasizes the need of thorough evaluation of the characteristic morphologic features of the aorta (which gives rise to brachiocephalic trunk, left carotid artery and left subclavian artery) and pulmonary artery (which bifurcates on its left and right branch), so as the transposition of the great arteries was not missed.